Ageing has been found to be related to increased reactive oxygen species resulting in increased oxidative stress within the body. This can contribute to decreased muscle strength, thereby increasing risk of injury such as falls and fractures, as well as a general reduction in quality of life.
As a result, the potential of substances with antioxidant properties, such as carotenoids, vitamin E and retinol, present an interesting opportunity for the prevention of this loss of strength. Whilst previous findings have reported an association between serum carotenoids and α-tocopherol with muscle strength, the studies are limited in numbers and low in validity as a result from methodologies used.
Using a sample of older adults from the National Health and Nutrition Examination Survey (NHANES) 2001–2002, researchers from Federal University of Uberlandia in Brazil conducted the present cross-sectional study to assess this relationship, hypothesising that higher serum levels of carotenoids, vitamin E and retinol would be associated with muscle strength.
“It is possible to suggest that an increased consumption of fruits and vegetables (mainly the α-carotene food sources) may be a protective factor for muscle strength in older adults,” concluded the researchers.
The US-based participants obtained from NHANES; a survey developed by the National Centre for Health Statistics assessing health and nutrition status, were screened according to eligibility criteria to select a final sample of 1172 of men and women aged 50-85 years from an original sample of 11,039.
Muscle strength was assessed by evaluating peak isokinetic knee extensor strength, whilst serum antioxidant levels were measured using high-performance liquid chromatography.
It was found that only serum α-carotene levels were positively associated with muscle strength in the observed sample, whilst no association was found with trans-β-carotene, cis-β-carotene, β-cryptoxanthin and vitamin E. These results suggest that the mechanisms of action vary by antioxidant type, with regards to muscle strength.
Applications for antioxidants
The protective effect of α-carotene observed in this study may result from its potentially greater antioxidant power, as observed in previous studies. “For example, an in vivo study showed that α-carotene seems to inhibit the proliferation of the human neuroblastoma cells about 10 times more than β-carotene,” said the researchers, despite the structural similarities of the compounds.
This may open future research into investigating specific antioxidant groups and their applications for health issues, with the potential to improve the accuracy and subsequent success of preventative and treatment interventions.
“The main food predictors of α-carotene are carrots and other root vegetables, bananas, oranges, and tangerines, but α-carotene is also correlated with the total consumption of fruits and vegetables,” said the researchers.
Yet, the inconsistencies in the data obtained here compared to those from previous studies, which demonstrate associations between other antioxidant types and muscle strength, suggest the need for further investigation. Whilst the sample was large and objective quantitative measurements were used, the cross-sectional methodology prevents the establishment of a causative relationship.
“Longitudinal studies or randomized clinical trials should be performed to confirm this hypothesis,” the researchers emphasised.
2022, 11(12), 2386; doi: 10.3390/antiox11122386
“Serum α-Carotene, but Not Other Antioxidants, Is Positively Associated with Muscle Strength in Older Adults: NHANES 2001–2002”
Authors: R.R. Bruno, et al.